Don’t Miss These 5 Bugs
Common houseplant pests can be tough to detect and may even disguise themselves as dust. With a broad palette, many don’t discriminate about which species they invade. The first sign may be a dusky finish on leaf surfaces, little flecks of dirt, or mold, which may be the pests themselves or their trail.
Outdoors, we have the advantage of natural predators like ladybugs, parasitic wasps, hoverflies, and lacewings that help control populations. Houseplants stressed by cultural factors like water fluctuations and low humidity are more likely to succumb to damage. The best management is to set them up with their key cultural requirements for the best growth.
Scouting and detecting pests early helps prevent insects from depleting nutrients, impacting growth, and transmitting diseases. Inspect new houseplants before bringing them inside to minimize introduction and spread. You may even want to isolate them for a couple of weeks before placing them near others. When bringing plants back inside for the fall and winter, give them a good look and rinse to avoid bringing insects indoors.
For pest prevention and for overall health, dust houseplant leaves occasionally. Dusting improves photosynthesis for energy to grow while limiting ideal situations that foster some of the most common bugs.
Mealybugs
Mealybugs are soft-bodied, sap-sucking insects that look like dust on houseplant foliage and stems. Their bodies are waxy, white, and fibrous like cotton. They move slowly and congregate on the undersides of leaves, along veins, and tucked away in joints.
In an infestation, you’ll see the insect along with yellowing, wilting, stunted growth, and general weakness and decline. With piercing mouthparts, they feed on sap and lay eggs in cellular tissues. The larvae feed as they hatch and continue the cycle.
Mealybugs leave behind a signature sticky “honeydew” waste. The residue can lead to unhealthy black fungus or sooty mold. Sooty mold develops in humid conditions and makes the foliage look dirty and unattractive.
Early mealy outbreaks are easy to control, but if not caught in time, they recur and are challenging to get rid of entirely.
Prevention
To prevent mealybugs, aim for consistent moisture and bright, indirect light for most houseplants (or the best cultural requirements based on each selection). Avoid fertilizing too much, as many pests enjoy tender new growth and high nitrogen levels. Excess fertilizer promotes both. Consistently cleaning your houseplants can assist in removing dust and pest egg sacs.
Treatment
Run a steady stream of water over the dusty houseplant dislodge the pests. Follow up with a cotton swab dipped in less than 70% isopropyl alcohol, wiping all surfaces. This treatment is effective at instantly reducing small populations. The aim is to deter mealybugs by displacing them (and their piercing mouthparts).
Spraying a horticultural soap or neem oil on both sides of the foliage controls infestations. Other plant-based insecticidal oils include garlic extract, clove, rosemary, mint, and cinnamon oils and are effective organic controls. Following label directions, more than one application may be necessary to eliminate the problem pests. Protect surrounding surfaces when treating indoor plants.
In prolonged infestations, it’s best to discard the unhealthy specimens to prevent the spread of mealybugs among houseplants.
Aphids
Aphids come indoors on infected plants, attached to clothing, or on the breeze through open doors and windows. The prolific reproducers flock to tender new growth. You’ll also find them under leaves and on stems of fresh shoots.
There are hundreds of species of these sap-suckers that feed on tissues. Their vast palette includes ornamentals, edibles, and houseplants, and they colonize in large numbers on the undersides of leaves.
Aphids have soft, pear-shaped bodies in light yellow, green, pink, brown, or black. With piercing mouthparts to mine for sap, they cause stress in high numbers. Infested plants may show curling foliage, yellowing (the entire surface or in spots), and stunted growth.
Relatives of mealybugs, aphids also leave behind shiny, sticky honeydew that leads to sooty mold. They’re vectors for spreading fungal spores and viruses. Symptoms of virus or fungal diseases like leaf spot, mottling, and distortion may appear after aphids are present.
Prevention
Watering consistently for evenly moist soils is the best preventative measure. Aphids gravitate toward drought-stressed specimens over healthy, well-watered ones.
Treatment
For early numbers, employ the stream of water bath. Or, wipe both sides of the leaves with a soapy cloth. Do this as part of ongoing maintenance with recurring aphids.
Since aphids congregate in high numbers, pruning off impacted sections may eliminate small infestations. Spraying a horticultural soap or oil on both sides of the leaves controls an outbreak. Additional applications may be necessary for eradication.
Thrips
Thrips are tiny insects with long, narrow bodies. Their color ranges from translucent white to yellow, brown, and black, and adults have fringed wings. Thrips feed on foliar tissues and can transmit viruses. As a response to their feeding, foliage may appear silvery with streaks or stippled, brown, and papery. Some thrips leave sooty spots on surfaces.
It’s easy to control damaging thrips early on and with regular scouting. If you aren’t sure if it’s thrips, gently shake stems over a piece of white paper and look for dark spots (the dislodged pests). Blue sticky traps, too, attract the bugs to determine an infestation. As a note, African violets are a thrip favorite.
Prevention
Rinse or wipe dust off houseplants to deter tissue-feeding pests. Winter brings drying conditions with heating and fireplace usage. If humidity is low, place the pot near a tray of pebbles filled with water to increase the immediate air moisture. Dust leaves as indeed to keep them free of particulates.
Treatment
Clip and dispose of affected sections when feasible. Neem and horticultural soaps treat infestations; coat all surfaces of foliage and stems at application. Spinosad, derived from a bacteria, is an organic treatment that disrupts their feeding and kills the insect.
Spider Mites
Spider mites multiply rapidly and cause a dusty, dull look to leaf surfaces. The minute sap-sucking pests live on the undersides of leaves. You may not see the tiny insects without a magnifying lens, but their fine webbing on stems and leaves is a sure sign. Two-spotted spider mites are the most common among houseplants.
Colonies gather along leaf veins and mid-ribs underneath. The females lay eggs, and the larvae quickly feed on sap and tissues. Adults feed and produce the tight webs.
With spider mites, foliage shows pale spots, light yellowing, and white stippling on surfaces. Foliage may become stiff and curl, leading to premature drop. Like thrips, dusting a stem over a sheet of paper may reveal the mites as tiny, moving dots to confirm infestation.
Prevention
Spider mites occur most in warm, dry, and dusty situations. Houseplants that experience drought stress from underwatering are most susceptible. To prevent spider mites, maintain evenly moist soils. Moisture fluctuations give them the opportunity to increase, further weakening the host plant.
Raise humidity in the immediate surroundings with the pebble tray method and keep soils evenly moist to avoid overly dry situations.
Treatment
If you detect spider mites, use the stream of water method, as with mealy and aphids. Prune away affected stems if possible. A horticultural soap or oil helps mitigate large populations.
Scale
Often overlooked, scale appear as little splotches or black, gray, or silvery dots underneath leaves and on stems. They pierce tissues to feed on sap and, as with mealybugs, scale, and aphids, you may notice a sticky residue. The residue coats the plants and may drip onto nearby surfaces or the floor surrounding the pot.
Scale look like little legless blobs, and adults stick to leaves and stems. While mobile in the nymph stage, they become stationary after molting (which lessens their ability to spread from pot to pot).
In scale outbreaks, leaves turn yellow, wilt, and drop, with stems dying back in heavy infestations. New growth may stunt or show deformities. Remove affected growth where feasible in severe cases.
Prevention
To prevent scale pests, keep houseplants dust-free. Wipe them occasionally or give them a bath during a regular watering session.
Treatment
For low numbers, remove them by hand with a cotton swab and alcohol rub. A soft toothbrush dipped in soapy water also helps to detach the bugs. Lastly, soaps and oils are effective in controlling nymph populations.
